Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1996-09-04
2000-01-11
Cooney, Jr., John M.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525454, C08F28304
Patent
active
060137398
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a coating composition comprising
The present invention also relates to processes for producing a multicoat protective and/or decorative finish on a substrate surface and to the use of the coating compositions in the sector of automotive refinishing.
BACKGROUND AND SUMMARY OF THE INVENTION
Multilayer coatings, especially two-coat metallic finishes, are produced in particular by the basecoat/clearcoat method. This method is known and is described, for example, in U.S. Pat. No. 3,639,147 and EP-A-38 127.
The basecoat/clearcoat method can be used to produce finishes whose superiority over one-coat finishes is manifested in an enhanced effect and in the possibility of producing finishes with more brilliant and more clean colors.
The basecoat which is applied first of all determines, depending on the nature, quantity and spatial orientation of the pigments employed, the color and, if appropriate, the effect (e.g. metallic effect or pearl luster effect) of the finish.
Following application of the basecoat, at least some of the organic solvents and/or at least some of the water are or is removed from the applied basecoat film in an evaporation phase. A nonaqueous, transparent topcoat is then applied to this predried basecoat (wet-on-wet method). Basecoat and topcoat are then dried together.
The applied transparent topcoat gives the two-coat finish gloss and fullness and protects the pigmented coat applied from chemical and physical attack.
Using the method under discussion, it is only possible to obtain high-quality two-coat finishes if the transparent topcoat applied does not adversely affect the applied basecoat in such a way that the optical effect is impaired (e.g. clouding). On the other hand, the transparent topcoat must have a composition which ensures that it adheres well to the basecoat after the drying process. Further important properties which the transparent topcoat obtained after the drying process is required to have are a high degree of transparency, very good topcoat appearance, good gloss and good mechanical properties such as hardness, mar resistance and elasticity. Not least among the requirements, the transparent topcoat obtained after the drying process must have a high resistance to climatic effects (e.g. fluctuations in temperature, moisture in the form of water vapor, rain and dew, radiation-induced stress, etc.) and to attacks by acids or other chemicals such as, for example, organic solvents.
JP-A-1-158079 describes nonaqueous transparent topcoats for two-coat finishes of the basecoat/clearcoat type, which contain a hydroxyl group-containing polyacrylate resin which is obtainable by polymerizing from 10 to 50% by weight of an adduct of a cyclic ester, for example .epsilon.-caprolactone with hydroxyethyl acrylate or methacrylate, from 0 to 40% by weight of a hydroxyalkyl acrylate or methacrylate and from 30 to 80% by weight of a copolymerizable vinyl monomer to give a polyacrylate resin having a hydroxyl number of from 60 to 160, an acid number of from 0 to 40 and a glass transition temperature of from -50 to +40.degree. C. The transparent topcoats described in JP-A-1-158079 give finishes which are in need of improvement, especially with respect to their acid resistance and adhesion.
JP-A-4-1254 discloses coating compositions which contain, in addition to a crosslinking agent, a hydroxyl group-containing polyacrylate resin which has been prepared using 4-t-butylcyclohexyl acrylate and/or 4-t-butylcyclohexyl methacrylate as monomer component. The hydroxyl group-containing monomer employed for the preparation of the polyacrylate resin comprises, in particular, hydroxyethyl acrylate and hydroxyethyl methacrylate. These coating compositions known from JP-A-4-1254 have the particular disadvantage, when used as a transparent topcoat over a basecoat, that the resulting coatings are of inadequate adhesion to the basecoat. Furthermore, the resulting coatings have a poor solvent resistance, a high swellability and a poor overcoatability.
F
REFERENCES:
patent: 4212347 (1980-07-01), Eastman
patent: 5136004 (1992-08-01), Bederke et al.
patent: 5195240 (1993-03-01), Shuster et al.
Brunnemann Michael
Rink Heinz-Peter
Rockrath Ulrike
BASF Coatings AG
Cooney Jr. John M.
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